Distorted and Deformed Crystals and Pseudomorphs

Distorted Crystals

These seldom approach perfection in their shapes but are more or
less distorted, since their faces have not all enjoyed an exactly
equal and perfect development. Probably faces develop unequally
due to their relationship to the source of supply of the solutions
carrying the atoms of which they are composed. Growing in confined
spaces, as most crystals do, some faces, or sides, are likely to
grow faster than others. Such crystals may appear to be drawn out,
shortened or flattened, but the corresponding angles between faces
are CONSTANT.

Deformed Crystals

These have been bent and twisted out of their normal shape, usually
by some later deforming force, so that the corresponding angles
between faces may DIFFER WIDELY. This, however, is not a common
occurrence.

Pseudomorphs

(from PSEUDO, meaning FALSE, and MORPH I meaning FORM). After the
original growth, if the chemical composition or the structure of
a crystal becomes altered without modifying or destroying its original
faces, the result is a crystal whose faces are unchanged but whose
internal structure has become that of an entirely different mineral.
The resulting crystal is known as a PSEUDO MORPH (pronounced SUE-doe-morf).
Tiger's eye is an excellent example. In this mineral the original
fibers, consisting of monoclinic crystals of crocidolite (pronounced
kro-SID-oh-lite), or blue asbestos, have been replaced by minute
grains of quartz that in mass, have retained the original external
form of the crocidolite, but each of which has assumed the internal
crystal structure for quartz.